Just moments before the Frenchman's strike, El Glorioso were reduced to 10-man after Jota was sent off for a second bookable offence. However, Barcelona failed to make the numerical advantage count and dropped more points, thereby extending their winless run in the league to four-games now.
On that note, here are the player ratings for Barcelona.
Neto - 6/10
Neto was barely tested in the match by Alaves, who spent most of the time in their own half. But the goalkeeper did make an embarrassing howler in the opening stanza that allowed Luis Rioja to put his side ahead, a goal that later proved decisive in the context of the match.
Sergi Roberto - 7/10
Defensively, Sergi Roberto had little to do. He instead amplified his attacking output, sending some incredible crosses into the Alaves box and also made five key passes - the most by any player in the match.
Gerard Pique - 7/10
Gerard Pique was sound in defence and also drew a foul out of Jota that got the latter sent off in the second half. However, the veteran defender must be kicking himself for missing a great chance in the dying moments that could've helped Barcelona clinch all three points.
Clement Lenglet - 7.5/10
Clement Lenglet showed excellent positional sense in defence and also charged out of his line on several occasions to drive the ball forward. He created a wonderful chance for Ansu Fati early on in the first half with a defence-splitting pass. However, in an interesting move by Koeman, Lenglet was hooked off at the break for a winger, Trincao.
Jordi Alba - 6.5/10
It was a rather quiet night for the marauding Jordi Alba, who could neither connect well with his attackers during his forays forward nor stood out defensively. Alba was subbed off for Sergino Dest in the 71st minute.
Sergio Busquets - 6/10
One of the poorest performers for Barcelona against Alaves, Sergio Busquets continues to lend credence to the common belief that he's a spent force now. He gave away possession in key areas and also misplaced passes early on. Not surprisingly, he was substituted at half-time.
Frenkie de Jong - 6.5/10
Frenkie de Jong was almost non-existent in the first half, apart from a moment when he headed an effort over the bar. After Busquets was taken off at the break, the Dutchman was forced to play further back and provide cover for the Barcelona defence.
Ousmane Dembele - 6.5/10
After his wonderful goal against Juventus in midweek, Ousmane Dembele was back to producing a no show. He struggled to get himself involved in the match as Alaves did a good job of keeping him in check. The Frenchman was also dispossessed a couple of times during the game.
Lionel Messi - 7.5/10
Lionel Messi, the Barcelona captain, was once again at the heart of the proceedings for his club but failed to inspire his side to a win. He saw one of his free-kicks cleared off the line and curled an effort narrowly wide of the post. The frustration of failing to score from open play clearly got to him.
Ansu Fati - 6.5/10
The Barcelona wunderkind turned 18 on the day but failed to celebrate his birthday with a goal. He came close on two occasions but saw both his efforts sail just inches wide of the post. Fati, however, did set up AntoineGriezmann for Barcelona's equaliser by pouncing on a loose ball.
Antoine Griezmann - 7/10
Antoine Griezmann must have heaved a sigh of relief to have finally opened his account for the season when he delicately chipped the ball over Pacheco for the match-salvaging equaliser for Barcelona. However, until then, the Frenchman was barely seen in the match, and even after his goal, Griezmann struggled to make any meaningful contributions in the attack.
Player Ratings of Barcelona substitutes
Miralem Pjanic - 7/10
Miralem Pjanic came on for the ineffective Busquets and brought some much-needed urgency to Barcelona's play. Pjanic connected with Messi and pushed his side forward with his excellent distribution skills. His ball control was superb, and he even tested Pacheco from range with a venomous shot.
Francisco Trincao - 7/10
Fracisco Trincao brought plenty of pace to Barcelona's game, running through the channels and laying the ball off to Lionel Messi and Antoine Griezmann. However, he was caught offside on a few occasions.
Pedri - 7.5/10
The 17-year old was one of three Barcelona substitutions at half-time and was arguably the best of the lot. His link-up play was top notch, and he created a bevvy of chances by laying brilliant crosses.
Sergino Dest - 6.5/10
Despite some impressive showings recently, Sergino Dest was dropped to the bench against Alaves. The young American was brought on for the final 20 minutes of the match in place of Alba but couldn't really make much of an impact. His shot off Messi's free-kick was parried away by Pacheco.
Martin Braithwaite - N/A
Martin Braithwaite came on for the final few minutes of the match, replacing Fati, but didn't see much of the ball.